It depends. I don't go around blocking people willy-nilly, but I've never understood why some people are so dead set against it.
My general policy when someone is being obnoxious (ie. spamming, making inappropriate jokes, repeatedly following and sitting/dancing on me) is to politely ask them to stop. If they persist and are clearly being deliberately annoying, I inform them that I'll block them, and if I need to after that I actually do (reporting first if they're breaking a rule). Then I unblock them a few days later and usually don't encounter them again anyway. Strangely, I've noticed that the majority of people seem to stop/leave if you just tell them you're going to block. Not sure why it should matter to them, but it happens a lot that I've seen.